/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.confignode.procedure.scheduler;

import org.apache.iotdb.confignode.procedure.Procedure;

import java.util.ArrayDeque;

/**
 * Simple scheduler for procedures
 */
public class SimpleProcedureScheduler extends AbstractProcedureScheduler {
    private final ArrayDeque<Procedure> runnables = new ArrayDeque<>();
    private final ArrayDeque<Procedure> waitings = new ArrayDeque<>();

    @Override
    protected void enqueue(final Procedure procedure, final boolean addFront) {
        if (addFront) {
            runnables.addFirst(procedure);
        } else {
            runnables.addLast(procedure);
        }
    }

    @Override
    protected Procedure dequeue() {
        return runnables.poll();
    }

    @Override
    public void clear() {
        schedLock();
        try {
            runnables.clear();
        } finally {
            schedUnlock();
        }
    }

    @Override
    public void yield(final Procedure proc) {
        addBack(proc);
    }

    @Override
    public boolean queueHasRunnables() {
        return !runnables.isEmpty();
    }

    @Override
    public int queueSize() {
        return runnables.size();
    }

    public void addWaiting(Procedure proc) {
        waitings.add(proc);
    }

    public void releaseWaiting() {
        runnables.addAll(waitings);
        waitings.clear();
    }
}
